In electric drives for hybrid and electric vehicles, usually these days, three-phase polyphase machines are used. In the operation of these polyphase machines, pulse-controlled inverters are used having field-oriented regulation. In such a field-oriented regulation, information is required on the rotational speed and the position of the rotor.
A method and a device are described in German Patent No. DE 10 2005 049 070 for the field-oriented regulation of a polyphase machine. The actual torque of the polyphase machine is ascertained, in this instance, and the actual torque ascertained is compared to a setpoint torque, and when there are deviations from the torque, the setpoint values for the flux-forming current and the torque-forming current are changed, so as to bring the actual torque into agreement with the setpoint torque. The actual torque is calculated using the measured phase currents and machine constants of the polyphase machine. Among other things, information is taken into account, in this instance, on the rotational speed of the rotor shaft of the polyphase machine. A control unit is used for carrying out the calculation processes mentioned and for controlling the switching elements of the pulse-controlled inverter, and it converts the measuring signals supplied to it into control signals for the switching elements of the pulse-controlled inverter.
To record the position and the rotational speed of the rotor, pulse generators may be used, for example, which have a specified angular offset with respect to one another and which scan a pulse generator wheel. The position ascertainment takes place by an evaluation of the signals supplied by the pulse generators.
If phase lines or pulse generator lines are mixed up by mistake when the pulse-controlled inverter and the polyphase machine are assembled, the rotor cannot start up in spite of a torque that is set to be sufficiently large.